Nowadays, mobile terminals provide various functions such as a wireless Internet function, electronic note function, multimedia photographing and reproducing function, and game player function, digital broadcasting function in addition to a basic communication function. Such a mobile terminal generally uses a battery for portability.
The battery of the mobile terminal requires electric charging. A method of charging the battery can be classified into wired charging and wireless charging. The wired charging method is generally used, however, a wireless charging system using an electromagnetic induction phenomenon has been developed. Such a wireless charging system applies power to a charging pad including a coil (hereinafter, a first coil) at the inside thereof, and charges a battery using an induced current generating in a coil (hereinafter, a second coil) included in a mobile terminal, or a battery using a magnetic field generating in the first coil. That is, the wireless charging system can easily charge a battery by positioning the mobile terminal on a charging pad generating a magnetic field. However, such a wireless charging system has different charging efficiency according to a location relationship of the first coil and the second coil. In other words, when the first coil and the second coil are positioned to correspond, the wireless charging system has the best charging efficiency. That is, the wireless charging system should be positioned at the mobile terminal at a specified location in order to sustain optimum charging efficiency. In order to solve the problem, conventionally, a method of mounting a plurality of first coils, or a method of largely forming the first coil in order to cover an entire charging pad area was used. However, such a conventional method has a problem that wireless communication performance is deteriorated due to an influence of a magnetic field generating by the first coil and because the magnetic field is induced in a high and wide area, performance and a lifetime of parts of a mobile terminal may be influenced. Therefore, a wireless charging system and method in which a magnetic field generated by the first coil does not deteriorate wireless communication performance of the mobile terminal and that secure stability of the mobile terminal and that optimize charging efficiency are requested.